Echoing down the corridors of eastern Ukraine’s Pokrovsk Perinatal Hospital are the loud cries of tiny Veronika.Born nearly two months prematurely weighing 1.5 kilograms (3 pounds, 4 ounces), the infant receives oxygen through a nasal tube to help her …

For years, global health officials have used billions of drops of an oral vaccine in a remarkably effective campaign aimed at wiping out polio in its last remaining strongholds — typically, poor, politically unstable corners of the world.Now, in a